Over the past two centuries, buildings with soft storey configurations have been widely constructed all over the world. Broadly, a soft storey building is a building having one or more floors with windows, wide doors, large unobstructed commercial spaces, or other openings in places where a shear wall, or other structural support, would normally be, or where a shear wall, or other structural support, is positioned on other floors above the soft storey, such that the soft storey has significantly lower stiffness and/or strength than the storeys above it. Providing space for parking, retail, storefront windows, shopping areas, and lobbies at the first floor of multi storey buildings are the architectural and social advantages of such buildings as is shown in FIG. 1. Many older buildings are already in existence with this, or similar, configurations. These soft-storey buildings are known to have an extremely poor seismic performance with a propensity for collapse at the first floor, or first few floors which define the soft storeys, and are considered as one of the most vulnerable building typologies commonly found in highly populated urban areas.
Since earthquake records have been recorded, it is estimated that over 8.5 million deaths and almost $2.1 trillion in damage have been reported all around the world. Considering the high contribution of soft storey buildings in the loss of life and money, it has been estimated that soft storey buildings were responsible for a few million fatalities and several billions of dollars of losses. For example, almost two thirds of units that were uninhabitable after the Northridge earthquake, just outside of Los Angeles in 1994, and a high percentage of the death toll were attributed to buildings having a soft storey. These problems with soft storey buildings are widely documented, and well known in the art.
Recently, the art has evolved to the development of more modern design procedures and codes that are intended to avoid column side-sway responses that lead to soft storey response that ultimately renders the building unusable. Measures have been introduced in building codes to address this problem by ensuring that new buildings possess relatively uniform strength and stiffness over the building height. For existing buildings with soft storeys, legislation may require the assessment and retrofit of the structure, and typical retrofit efforts will typically increase the strength and stiffness of the soft storey. However, this does not necessarily reduce the expected total damage and financial losses in the entire building, as some degree of side-swaying still occurs. In addition, traditional retrofitting approaches, such as added reinforced concrete walls or steel braces, not only pose several obstacles to the architectural functionality of these structures, but also greatly increase the design loads that must be accommodated in the retrofitted building. Most, if not all, of these retrofitting approaches of the prior art include substantial modifications to the building structure, often times restricting the use of the soft storey prior to the retrofit, shown schematically in FIG. 2. In addition, many retrofits are cost-prohibitive and fundamentally alter the architecture of the building or the nature of the soft storey itself.
There is accordingly a need in the art of an alternate solution to mitigating the effects of seismic events on a building structure having at least one soft storey.